In the past, hand-held paint spray guns, sometimes known as “cup guns” utilized a single orifice spray tip to atomize paint for spraying. The atomization pattern delivered by such tips were characterized by a relatively gradual transition in spray pattern from dense coverage (analogous to the “umbra” of a shadow) in the center of the spray pattern to sparse coverage (analogous to a “penumbra”) in the peripheral region of the spray pattern. Such a gradually decreasing coverage spray pattern is undesirable since it has a poorly defined boundary between “coverage” and “no coverage,” causing either overspray beyond the desired (dense) coverage or incomplete or sparse coverage where dense coverage is desired. Because the dense central coverage is delivered concurrently with the sparse peripheral coverage, it has heretofore been necessary to mask a relatively wide region adjacent to the area desired to be spray painted, because of the gradually decreasing density in the peripheral region of the spray pattern. In addition, such prior art atomization patterns were also characterized by the presence of undesirably small sized atomized particles (sometimes called “fines”) in the peripheral region (“penumbra”) of prior art spray patterns. Such uncombined fines in the peripheral region of the spray pattern are undesirable, since they are prone to cure or dry before reaching the surface to be coated, becoming undesirable overspray particles that do not adhere the surface being treated, resulting in waste product of the material being sprayed, and thus can be a contributing factor to decrease the transfer efficiency of the paint spraying process.
One prior art system, Nespri-TEC, uses airless paint spray equipment to apply a special coating material. Equipment for that system is offered by J. Wagner GmbH of Otto-Lilinethal Strasse 18, 88677 Markdorf, Germany, under the trademark NESPRAY. Coating materials for that system are offered under the trademarks AmphiSilan, Nespri FiXX, and Nespri Silan by Caparol Farben Lacke Bautenschutz GmbH of Rossdofer Strass 50, 64372 Ober-Ramstadt, Berlin, Germany. However the Nespri-TEC system differs from the present invention in that it requires special coating material that, in turn, requires the equipment to heat the coating material to control the viscosity. The present invention does not require any special thinners and does not require any special coating material. Conventional paint (and similar conventional coating materials) can be used with the present invention. In addition, the coating material does not need to be heated in the practice of the present invention, unlike the prior art Nespri-TEC system. Finally, the present invention may be practiced with non-converging centerline spray patterns, as well as with converging centerline spray patterns. The NESPRAY equipment has only converging centerline spray patterns.
The present invention also overcomes the shortcomings of conventional prior art cup guns by providing a more sharply defined spray pattern, decreasing relatively rapidly from dense coverage in the central region to no coverage at the periphery of the spray pattern delivered by the present invention. The present invention increases the overall proportion of “fines” in the central region of the spray pattern, and at the same time reduces the proportion of fines in the peripheral region. It is to be understood that fines present in the central region effectively aid the coating process by recombining to form larger atomization particles in the central region of the spray pattern using the present invention. The present invention thus increases the transfer efficiency of and reduces waste products from the spraying process.